1. Field of the Invention
This invention relates to chemicals for controlling plant virus diseases and also to a control method using such chemicals.
2. Description of the Prior Art
It is known that the plants such as tobacco, tomato, Spanish paprika, potato, cowpea, French bean, cucumber, water melon, strawberry, melon, Chinese cabbage, radish and the like, which are cultivated in various manners of culture such as fieled culture, glasshouse culture, etc., tend to suffer from mosaic diseases and dwarfing diseases to plant viruses such as a tobacco mosaic virus (hereinlater abbreviated as TMV), cucumber mosaic virus (hereinlater abbreviated as CMV), cucumber green mottle mosaic virus (hereinlater abbreviated as CGMMV), potato virus X (hereinlater abbreviated as PVX), lettuce mosaic virus (hereinlater abbreviated as LMV), melon necrotic spot virus (hereinlater abbreviated as MNSV) and the like, thus frequently incurring a great deal of damage to these plants. Since these plant viruses generally exist in various plants, weeds, seeds, soils, roots remaining in soil, the plant suffers readily contagion to the viruses by the suction of plant juice by the insects, by artificial contact (such as with farm appliances, hand, or clothes), or by the contact with the virus-containing soil during transplantation or planting, etc. If a primary contagion takes place, there is a danger that the plant virus spreads throughout the field or other culture systems by the artificial contact such as the farming work.
Various chemicals for controlling such plant virus diseases are known including: antibiotics and base in nucleic acid-like substances both of which have a function of suppressing multiplication of plant viruses; and the juices of plants such as dyer's grape (Phytaracca decandra), goosefoot, carnation, etc., and polymeric materials derived from living body such as casein, alginic acid, etc both of which have a function of preventing contagion of plant viruses to the plants. However, most of the former substances exhibit toxicity against man and domestic animals as well as plants and thus have never been used in practical application. The latter substances are of natural origin and thus a difficulty is encountered in mass-producing the substances having uniform composition. Only one instance which has been practically used is a chemical containing sodium alginate as a principal component (wettable powder of alginic acid: Registration No. 13440 at the Minister of the Agriculture and Forestry, Japan).
Therefore, if a plant has been once infected with a disease in the culture field, the secondary contagion is generally prevented by a passive manner that the infected plants are removed and burnt up as soon as we find.
We have made an intensive study to develop an agricultural chemical for controlling plant virus diseases which is innoxious and high in efficacy and, as a result, found that polymers of dialkylaminoalkyl acrylate derivatives or dialkylaminoalkyl methacrylate derivatives show high activity of controlling plant virus diseases.